RNA processing and transport RNA degradation Translation Gene Expression is regulated due to environmental and developmental cues: DNA packaging Transcription RNA processing and transport RNA degradation Translation Post-translational Fig 16.1

For life to exist, the information (genes) must be passed on.

The Cell Cycle Fig 7.23

DNA replication precedes cell division

DNA replication starts at the origin of replication

Eukaryotic initiation of replication Fig 7.24

DNA replication starts at the origin of replication Helicase unwinds/separates the two strands of DNA.

DNA replication starts at the origin of replication The DNA is copied

The DNA is copied DNA replication starts at the origin of replication More unwinding, more copying

DNA replication starts at the origin of replication The DNA has now been copied. There are now two double-stranded DNAs

DNA polymerase can only use some DNA as template Completely single stranded 3' 5' Polymerase inactive G A A T C T G C Completely double stranded 3' 5' G A A T C T G C Polymerase inactive C T T A G A C G 5' 3' Single strand as template plus 3' end to start synthesis Figure: 12.8 Caption: When DNA templates are completely single-stranded or double-stranded, no synthesis occurs. The DNA polymerases work only when there is a single-stranded template and a 3’ hydroxyl group available, as shown here. 3' 5' G A A T C T G C Polymerase active C T T 5' OH 3'

Fig 7.17

How do cell’s stitch together Okazaki Fig 7.17

Proteins at work at the replication fork Fig 7.19

Gyrase untangles DNA Fig 7.19

Fig 7.16

Fig 7.22

Sometimes errors are made.

Error Luckily, errors can be repaired. As they occur by DNA polymerase

How does E. coli know which strand is new?

Errors are made during DNA replication 3,000,000,000 (3 billion) base pairs/human cell with 1 error/1 billion base pairs not repaired = (average) ~6 errors each time DNA is replicated

Not all errors get repaired. These are mutations.

Telomeres are non-gene DNA at the ends of DNA strands.

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are shortened during DNA replication.

The problem of replicating ends Fig 7.25

Telomere lengthening by telomerase Fig 7.26

Elongation of complementary telomere strand Fig 7.26

The telomere forms a protective cap on the end of the DNA with several cap proteins Fig 7.27

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are shortened during DNA replication, and also by DNA damage.

Telomeres are non-gene DNA at the ends of DNA strands. Short telomeres will cause cells to stop replicating or cell death. The critical size is unknown.

Human Life Cycle high levels of telomerase very little telomerase

Why not produce telomerase all of the time? high levels of telomerase very little telomerase

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are shortened during DNA replication, and by DNA damage. Short telomeres will cause cell senescence or cell death. Telomere size is a measure of mutations.

Do telomere dynamics link lifestyle and lifespan? Pat Monaghan and Mark F. Haussmann TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length varies in different parts of adults: Telomere length varies in different parts of adults: telomeres - mitosis stomach & blood cells....short - often muscle & brain……….long - rare liver & kidney……..short - rare gametes……long

Telomeres are non-gene DNA at the ends of DNA strands. Telomeres are more sensitive DNA damage, and may act as a sensor for overall DNA damage level in a cell.

Does telomere length indicate longevity?

Telomere length in red blood cells of different birds Zebra finch Age (years) Fig. 1 TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length in red blood cells of different birds common tern Age (years) Fig. 1 TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length in red blood cells of different birds albatross TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length in red blood cells of different birds Leach’s storm petrel Fig. 1 TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length in red blood cells of different birds, different species have different patterns of telomere length and age Zebra finch common tern albatross Leach’s storm petrel Fig. 1 TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length in white blood cells of different aged people Telomere length in white blood cells of different aged people. Telomere length generally declines, but there is wide variability Fig. 2 TRENDS in Ecology and Evolution Vol 21 pg 47

Telomere length and mortality in people over 60 years old upper 50% of telomere length proportion surviving % lower 50% of telomere length years after initial assessment THE LANCET • Vol 361 • pg 393

Telomere length may indicate biological age. Early stress may cause premature telomere degradation.